Without limiting the scope of the invention, its background is described in connection with a fully implantable device for direct cardiac compression and aortic compression. During a cardiac cycle, the heart expels oxygenated blood into the aorta as its left ventricle contracts (i.e., during systole) and, thereafter, receives a backflow of arterial blood into the coronary arteries as its left ventricle relaxes (i.e., during diastole). The systolic pumping of blood into the aorta requires the myocardium to overcome the static pressure of blood that is already in the aorta. A healthy heart is typically able to perform both of these functions effectively. However, a weakened or failing heart may be unable to perform the work required to fully overcome the static pressure of blood already in the aorta, thereby resulting in less ejection of oxygenated blood into the aorta during systole and less backflow of oxygenated blood into the coronary arteries during diastole. There are various methods of providing assistance to the failing myocardium.
Direct cardiac compression devices are generally known as disclosed first by Anstadt and later by Criscione and are effective in providing assistance to the failing myocardium by generally adding external pressure to help the heart muscle to contract. Generally these devices include a jacket positioned around the heart and containing inflatable bladders that are inflated to coincide with contraction of the myocardium during systole. Operation of such device is supported by a driver configured to inject fluid through a drive line to cause the bladders to expand and withdrawal of fluid during diastole causes the bladders to collapse in preparation for the next systole of the heart. The presence of the drive line exiting the subject is generally undesirable as it may be a source of infection, especially for patients requiring long-term or permanent support. One difficulty associated with injecting and removing a certain volume of drive fluid is the changing volume of the drive system. This changing volume of the drive system makes an implantable driver with changing internal volume problematic, due to the positioning of the device inside the subject so as to not periodically compress surrounding tissues.
In addition, counterpulsation devices are generally known to include an external pneumatically driven intra-aortic balloon pump that drives gas to and from an intra-aortic balloon. Implantable systems are also known and include an external aortic compression chamber attached to the ascending aorta where an injection of the drive fluid inside the chamber causes the aorta to compress, while withdrawal of drive fluid causes the aorta to relax to create a counterpulsation effect. Other implantable systems include an expandable chamber surgically attached to the descending aorta of the subject to cause its compression and expansion upon respective injection and withdrawal of the drive fluid by a fluid driver. The timing of inflation and deflation of a counterpulsation device is aligned with the diastole of the heart: the device is inflated at onset of diastole and deflated prior to or at systole.
U.S. Pat. No. 7,766,813 entitled, “Methods, devices and systems for counterpulsation of blood flow to and from the circulatory system,” discloses counterpulsation methods and systems for assisting the heart of a patient involve, for example, coordinating the operation of a pulsatile pump to suction blood from an artery through a first conduit while the heart is in systole and expel the blood into the first conduit and the artery while the heart is in diastole, the entire contents of which are incorporated herein by reference.
U.S. Pat. No. 7,347,811 entitled, “Heart assist device utilizing aortic deformation,” discloses providing counterpulsation heart assist by deforming the aorta, the entire contents of which are incorporated herein by reference. The deformation pressure is applied by cyclically, preferably in synchrony with the diastolic period of the heart. The deformation pressure may be applied to the outer wall of the aorta or to a patch covering a resected opening in the wall of the aorta.
U.S. Pat. No. 8,444,545 entitled, “Dual-pulsation bi-ventricular assist device,” discloses a ventricular assist device which comprises a sac for wrapping around a portion of a heart, the sac having one or more inflatable chambers for compressing the heart when the chambers being inflated and a blood outlet made to an aorta, the blood outlet being the sole opening in the human blood path in the vicinity of heart, wherein during a systolic phase the inflatable chambers inflate while blood flows out of the aorta through the blood outlet, and during a diastolic phase the inflatable chambers deflate while blood flows into the aorta through the blood outlet, the entire contents of which are incorporated herein by reference.
U.S. Pat. No. 4,813,952 entitled, “Cardiac Assist Device,” discloses a muscle-powered pump to assist the natural heart, the entire contents of which are incorporated herein by reference. The device comprises an oblate, spheroidal-shaped pumping chamber surrounded by innervated muscular tissue. The device may be coupled to the ventricle and descending aorta with valves and be stimulated in synchrony with the natural depolarization of the heart or the device may be inserted into the descending aorta and used as a counterpulsation device. In this application, the innervated muscle is stimulated after a brief delay from the natural cardiac depolarization.
Another device that may be used to increase myocardial blood flow in patients whose cardiac output is compromised due to heart failure or cardiac insufficiency and decreases the workload of the heart, through counterpulsation is an intra-aortic balloon pump. Intra-aortic balloon counterpulsation is a technique which causes more arterial blood to enter the coronary arteries (and thus more blood flow to the myocardium) during diastole (less flow work) and decreases the amount of work that the heart must perform during systole (less pressure work). By increasing coronary blood flow, the myocardium receives more oxygen, thereby allowing the heart to pump more effectively and increasing the cardiac output that occurs with each heartbeat (i.e., the “stroke volume”). The intra-aortic balloon counterpulsation comprises a balloon catheter that is percutaneously insertable into the aorta and a control console that is attached to the balloon catheter. A computer or controller within the control console receives the patient's electrocardiogram and causes the intra-aortic balloon to be inflated during diastole (when the heart muscle relaxed) resulting in increased back pressure within the aorta and increased blood flow into the coronary arteries, and deflated during early systole (during a phase known as “isometric contraction”) resulting in a reduction of intra-aortic pressure against which the heart must pump. In this way, the intra-aortic balloon pump improves blood flow to the heart muscle and reduces the workload of the heart muscle. Additionally, intra-aortic balloon pump counterpulsation has been demonstrated to improve peripheral or systemic arterial perfusion. Although the mechanism by which intra-aortic balloon pump counterpulsation improves peripheral or systemic profusion is not well understood, it is believed that inflation of the intra-aortic balloon during diastole serves to facilitate peripheral runoff (sometimes referred to as the intrinsic “Windkessel” effect) which then augments peripheral perfusion.